An increasingly large number of automobiles are equipped with a passive restraint system which employs an inflatable air bag in case of a vehicle crash by detecting a large acceleration or deceleration of the vehicle. Such an inflatable bag is normally installed inside a central part of a steering wheel for protecting the vehicle operator. To protect the vehicle occupant sitting next to the vehicle operator, an inflatable bag is normally installed inside a part of the instrument panel opposing the vehicle occupant.
An air bag system adapted to be installed in an instrument panel normally includes a casing extending laterally and having a certain depth. The inner or lower end of the casing is securely attached to a part of the vehicle body panel, such as a stiffener, and the upper surface of the casing is designed so as to be flush with the surrounding surface of the instrument panel. When the air bag is deployed, the resulting reaction will produce a torque which tends to turn the air bag casing around the lower end of the casing. Therefore, it is necessary to secure the upper end of the casing to prevent an undesirable movement of the casing.
It is conceivable to provide a bracket adjacent to the upper end of the casing, and securely attach the upper end of the casing by using threaded bolts or other fastening means. However, it will increase, not only the material cost, but also the amount of work required for the assembly work.